Marine biotoxins cause GI and neurological syndromes by predominantly which mechanism?

• A. Blocking voltage gated sodium channels in heart/muscle/nerve tissue
• B. Inhibiting acetylcholinesterase
• C. Activating potassium channels
• D. Blocking calcium channels

Answer: (A)

Blocking voltage-gated sodium channels on nerve and muscle membranes. Toxins like tetrodotoxin and saxitoxin bind to these channels and prevent sodium influx, stopping depolarization and the propagation of action potentials. Without nerve signals moving properly, you get the rapid neurological symptoms (numbness, tingling, dizziness, weakness, dysphagia, ataxia, potential paralysis) often accompanied by GI symptoms. The other mechanisms would produce different symptom patterns (for example, acetylcholinesterase inhibition causes cholinergic excess; potassium channel activation hyperpolarizes cells; calcium channel blockade reduces transmitter release), so they don’t fit the typical marine biotoxin picture as well.